Home history Louis D. Stevens Jr. Louis D. Stevens, Jr.
The pioneering engineer co-invented the first magnetic disk hard drive system
Portrait of Louis Stevens smiling

Louis D. Stevens Jr. was a pioneering engineer who made historic contributions to the invention of a unique magnetic disk storage device. The invention became a vital component of the IBM 305 RAMAC machine, unveiled in 1956, which was the progenitor of every hard-drive disk created since.

Before this breakthrough, data for computer processing had been stored on punched cards, paper tapes, magnetic tapes and magnetic drums. None of those could match the combination of storage density and lightning-fast direct access that the magnetic disk drive would eventually provide. The advance cemented Stevens’s place as a trailblazer in the history of computing.

His mother’s flair for creative problem-solving
A contributor to IBM’s first electronic computer

Born in Post, Texas, in 1925, Stevens always credited his mother with providing a flair for creative problem solving. She taught him that he could accomplish anything he applied himself to, and she often called on him to fix broken household items, including her few electrical appliances. He joined the US Marine Corps in 1943 and attended Radar Technician School, where he first encountered electrical engineering. With support from the GI Bill and earnings from his wife, he secured a bachelor’s degree in the field from Texas Tech University and a master’s from the University of California, Berkeley.

Stevens began his 35-year career with IBM in 1949 in Poughkeepsie, New York, and played a significant role in the development of the input-output unit for the 701 Electronic Data Processing Machine, IBM’s first electronic computer. Formally announced in May 1952, the 701 comprised 274 assemblies executing all the system’s computing and control functions by means of electronic pulses emitted at speeds of up to 1 million per second.

That same year, the company sent Stevens to help establish an experimental lab in San Jose, California, then a small town but the eventual heart of Silicon Valley. Team leader Reynold B. Johnson tapped Stevens to serve as his top lieutenant with an emphasis on recruiting applicants for an intentionally very lean and efficient ensemble.

Scaling RAMAC
From inspiration to mass production

In 1953, Johnson promoted Stevens to senior engineer and made him manager of the RAMAC project. In that role — and with the contributions of colleagues William Goddard and John Lynott — Stevens led the effort that changed the future of technology.

A team of roughly 50 engineers examined the cumbersome process that computers used to access data, which involved running a stack of hole-punched cards through a machine and shuffling linearly through the data. Other attempts at random-access retrieval had proven insufficient. The team essentially had to draft blueprints while it was building the structure.

“There were problems to be solved,” Stevens later recalled. “But I think for most of the basic problems, we at least had laboratory-level answers. We didn’t have production-level answers. … Questions came up like, how were we going to make that many disks, and how were we going to do the other things related to mass production?”

After four years, the team revealed an historic solution. The IBM 305 RAMAC — or simply RAMAC, as it came to be known — was the first computer to use a random-access disk drive. The team had magnetized aluminum disks by coating them with iron oxide paint. Magnetic spots on the disk represented characters of data, and a magnetic arm, akin to a record player needle, would read the spots as the disks rotated at blinding speed. 

Opening the door to relational databases

Pre-RAMAC, computer information retrieval took hours or even days. RAMAC could fetch and manipulate data exponentially faster — in seconds. It was a massive leap in speed and efficiency that made the relational database possible. For the first time, the average computer user had the ability to quickly and easily harness data. This democratization of information access changed the relationship between businesses and computers and laid the groundwork for everything from spaceflight and ATMs to search engines and e-commerce.

Stevens subsequently received a succession of promotions and was eventually named manager of the IBM Research lab in Los Gatos, California, in 1965. He retired in 1984.

In 2008, in recognition of his contributions to the development of the magnetic disk drive, Stevens was inducted into the National Inventors Hall of Fame. Stevens had eight filed invention patents, and, with Goddard and Lynott, he received US Patent 3,134,097 for the “Data Storage Machine.” Stevens passed away in 2009, at the age of 84, in Aptos, California.

Before RAMAC, computer information retrieval took hours or even days
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